1. Field of the Invention
The present invention relates to a semiconductor device having a passivation layer.
2. Description of the Related Art
In a semiconductor device, a multi-layer configuration bas been used as a passivation layer.
A first prior art passivation layer includes a double layer configuration formed by a phospho silicate glass (PSG) layer and a silicon nitride layer formed thereon. This will be explained later in detail.
In the first prior art passivation layer, however, since water penerates through very small defects in the silicon nitride layer and is absorbed in the PSG layer, metal connections directly in contact with the PSG layer may be eroded by the water absorbed in the PSG layer. Also, two different kinds of insulating layers used in the passivation layer require different manufacturing apparatuses, thus increasing the manufacturing cost thereof.
A second prior art passivation layer includes a triple layer configuration formed by a lower silicon nitride layer, a PSG layer formed thereon, and an upper silicon nitride layer (see JP-A-SHO62-128128 and JP-A-SHO62-242331). As a result, the lower silicon nitride layer prevents water absorbed in the PSG layer from penetrating into metal connections beneath the lower silicon nitride layer. Also, the mechanical strength of the passivation layer is enhanced as compared with the first prior art passivation layer. This will be also explained in detail.
In the second prior art passivation layer, however, since the PSG layer has deteriorated step coverage characteristics, it is impossible to thicken the lower silicon nitride layer, so that the prevention of penetration of water into the metal connections is insufficient. Also, two different kinds of insulating layers used in the passivation layer require two different manufacturing apparatuses, thus increasing the manufacturing cost.
A third prior art passivation layer includes a double layer configuration formed by a fluorine-including silicon nitride layer and a silicon nitride layer formed thereon (see JP-A-SHO62-174927). As a result, deterioration of semiconductor elements formed beneath the passivation layer due to the diffusion of hydrogen can be avoided, and simultaneously, erosion of metal connections beneath the passivation layer can be avoided by using the water resistance characteristics of silicon nitride.
In the third prior art passivation layer, however, since the fluorine-including silicon nitride layer reacts with water (H.sub.2 O) to generate hydrogen fluoride (HF), metal connections beneath the passivation layer are eroded by the hydrogen fluoride.